Performance comparison of local area video streaming systems

The performance of our Quality Oriented Adaptation Scheme (QOAS) for multimedia streaming in local networks is compared with other existing solutions (TFRCP, LDA+, and non-adaptive). This comparison is done in terms of bandwidth utilization, number of concurrent clients, loss rate, and end-user perceived quality. Simulation results show that for the same average end-user quality, our QOAS system can accommodate a significantly higher number of simultaneous clients while also having higher bandwidth utilization. For the same number of clients, the average end-user quality is always higher for QOAS than for the other solutions studied.     

Evaluation of registration methods on thoracic CT: the EMPIRE10 challenge

EMPIRE10 (Evaluation of Methods for Pulmonary Image REgistration 2010) is a public platform for fair and meaningful comparison of registration algorithms which are applied to a database of intrapatient thoracic CT image pairs. Evaluation of nonrigid registration techniques is a nontrivial task. This is compounded by the fact that researchers typically test only on their own data, which varies widely. For this reason, reliable assessment and comparison of different registration algorithms has been virtually impossible in the past. In this work we present the results of the launch phase of EMPIRE10, which comprised the comprehensive evaluation and comparison of 20 individual algorithms from leading academic and industrial research groups. All algorithms are applied to the same set of 30 thoracic CT pairs. Algorithm settings and parameters are chosen by researchers expert in the configuration of their own method and the evaluation is independent, using the same criteria for all participants. All results are published on the EMPIRE10 website (http://empire10.isi.uu.nl). The challenge remains ongoing and open to new participants. Full results from 24 algorithms have been published at the time of writing. This paper details the organization of the challenge, the data and evaluation methods and the outcome of the initial launch with 20 algorithms. The gain in knowledge and future work are discussed.     

Modal Analysis of the Quasi-Optical Performance of Phase Gratings

This paper is concerned with the analysis of phase gratings as passive quasi-optical multiplexing devices. One important application of such components is in the local oscillator injection chain of heterodyne array receivers. Gaussian beam mode analysis can be applied as a powerful tool when modelling the optical performance of phase gratings in a real submillimeter system of finite throughput and bandwidth. In our experimental investigations we have concentrated on the Dammann Grating (DG) which is a binary optical component and thus straightforward to manufacture. A number of quartz gratings were fabricated and carefully tested to evaluate the practical limitations of such quasi-optical components. Because of its convenient refractive index quartz can be used to produce gratings with very low reflection losses. The results presented confirm DGs to be particularly suitable multiplexers for sparse arrays of finite bandwidth.     

On the feasibility of using an atmospheric discharge plasma as an RF antenna

The plasma produced by a laser-guided, electric discharge in the atmosphere has been formed in the shape of a folded monopole antenna with a characteristic frequency of 112 MHz. This plasma antenna has been used to transmit and receive signals at 112 MHz. While the plasma remained conducting, the signal transmitted from, and received on, the plasma antenna was within -1pm1dB of that transmitted from and received on a "standard" copper folded monopole antenna of the same size. During this time the signal transmitted from, and received on, the plasma antenna also remained approximately constant in amplitude (fluctuationssim pm1dB). This useful lifetime of the plasma antenna was varied fromsim 200 mus togeq 2000 mus by changing the dration of the electric discharge sustaining the plasma columns. In these experiments, the noise from the plasma antenna was not distinguishable from that developed using a copper antenna, but in both cases the noise was much larger than the true thermal noise background.     

Monitoring hacker activity with a Honeynet

The Honeynet Project was founded by 30 US based security professionals with the intention of researching the techniques, tools, tactics and motives of hackers and the ‘blackhat’ community in general. A Honeynet Project is an all volunteer, non‐profit organization committed to sharing and learning the motives, tools, and tactics of the hacking community. It is comprised of a number of information security professionals dedicated to honeynet research and information security. This paper outlines the technical configuration of a honeynet, presents some of the key attacks on the honeynet to date and provides recommendations for securing networked systems. Copyright © 2005 John Wiley & Sons, Ltd.     

Mesoporous Silicon‐PLGA Composite Microspheres for the Double Controlled Release of Biomolecules for Orthopedic Tissue Engineering

In this study, poly(dl ‐lactide‐co‐glycolide)/porous silicon (PLGA/pSi) composite microspheres, synthesized by a solid‐in‐oil‐in‐water (S/O/W) emulsion method, are developed for the long‐term controlled delivery of biomolecules for orthopedic tissue engineering applications. Confocal and fluorescent microscopy, together with material analysis, show that each composite microsphere contained multiple pSi particles embedded within the PLGA matrix. The release profiles of fluorescein isothiocyanate (FITC)‐labeled bovine serum albumin (FITC‐BSA), loaded inside the pSi within the PLGA matrix, indicate that both PLGA and pSi contribute to the control of the release rate of the payload. Protein stability studies show that PLGA/pSi composite can protect BSA from degradation during the long term release. We find that during the degradation of the composite material, the presence of the pSi particles neutralizes the acidic pH due to the PLGA degradation by‐products, thus minimizing the risk of inducing inflammatory responses in the exposed cells while stimulating the mineralization in osteogenic growth media. Confocal studies show that the cellular uptake of the composite microspheres is avoided, while the fluorescent payload is detectable intracellularly after 7 days of co‐incubation. In conclusion, the PLGA/pSi composite microspheres offer an additional level of controlled release and could be ideal candidates as drug delivery vehicles for orthopedic tissue engineering applications.     

The DTX-240D digital circuit multiplication system

This paper describes the DTX-240D digital circuit multiplication system (DCMS) offered by ECI Telecom. It will accept up to 240 × 64 kb/s trunks carrying either 64 kb/s voice, voice band analogue non-speech signals, or digital data for transmission over a 2·048 Mb/s digital link. Over 1000 are currently ‘on-line’ and carrying traffic. The system comprises a pair of terminals, one on each side of the interterminal digital link (bearer). It will normally operate in the network at a concentration ratio of 5:1, in which case 150 × 64 kb/s trunks, carrying voice, voice band data or digital data can be concentrated into one 2·048 Mb/s bearer. The users are able to increase the number of trunks up to 240 per 2·048 Mb/s bearer, when time zone differences cause a spread of busy-hour traffic carried on a single system. Each terminal will normally be located at an international switching centre (ISC) but may also be located at an earth-station. The system uses a DSI (digital speech interpolation) stage providing a 2·5:1 multiplication, followed by an additional 2:1 multiplication by means of ADPCM (adaptive differential pulse code modulation). In addition, the VBR (variable bit rate) technique is used to prevent clipping, due to overload congestion. The system can also be used with 1·544 Mb/s digital bit streams (trunk side or bearer).     

An Analysis of SAFER

We investigate some of the algebraic properties of the SAFER block cipher when the message space is considered as a Z -module. In particular, we consider the invariant Z -submodules of the PHT layer and show how these invariant Z -submodules give potential cryptographic weaknesses. Received 12 June 1995 and revised 22 July 1997     

Modal analysis of partially coherent submillimeter-wavequasi-optical systems

We consider the modal analysis of partially coherent submillimeter-wave quasi-optical systems. According to our scheme the cross-spectral density at a plane is expanded as a sum of partially coherent propagating free-space modes. The coherence matrix, the elements of which are determined by evaluating bimodal overlap integrals, completely describes the state of the field at a plane. The coherence matrix can be traced through an optical system to another plane by means of a scattering matrix. Whereas diagonalizing the scattering matrix gives the natural modes of the optical system, diagonalizing the coherence matrix gives the natural modes of the field. We demonstrate the technique by studying the behavior of Gaussian beam telescopes when the field at the source plane is completely incoherent     

10-GHz 1.3-ps pulse generation using chirped soliton compression in a Raman gain medium

The authors demonstrate a novel pulse compression technique that is capable of producing high-quality 1.3-ps pulses at a repetition rate of 10 GHz. The technique begins with 20-ps pulses carved by a commercially available external modulator and achieves up to 15-fold compression using a combination of phase modulation and distributed Raman amplification. Unlike adiabatic soliton compression, the scheme takes advantage of an exact solution to the nonlinear Schrodinger equation for chirped soliton evolution. As such, high-quality low-pedestal compressed pulses can be produced in a shorter span of fiber than would be needed for adiabatic compression. Because the system uses external modulation, the source is inherently tunable. Furthermore, the degree of pulse compression can be adjusted by varying the amount of Raman gain and phase modulation.